Rabid Grannies aka Les Mémés Cannibales is a 1988 Belgian horror film directed by Emmanuel Kervyn. It opens as two elderly sisters invite their nieces and nephews to a dinner party in celebration of the sisters’ upcoming birthdays. The one nephew who is not invited is the ostracized black sheep of the family whose devil-worshipping activities have resulted in his being removed from the sisters’ inheritance. The rest of the guests are merely putting in time; they are actually only waiting for their aunts to die, leaving them amply endowed via their respective inheritances.
Unfortunately for all but the aunts, the nephew sends a party gift that turns the scene into a frolic of the macabre and ruins the party: under the gift’s power, the aunts turn into cannibals and proceed to eat up all of their guests!